KR20200093365A - Pouch-type secondary battery and method for manufacturing the same - Google Patents

Abstract

The present invention provides a pouch-type secondary battery capable of improving mechanical properties of a pouch-type secondary battery and a method of manufacturing the same. More particularly, the pouch-type secondary battery comprises: an electrode assembly; a lower cladding receiving the electrode assembly and including a pouch cladding with sealed edges, wherein the electrode assembly is placed on the pouch cladding; and a metal layer which includes a receiving portion accommodating at least a portion of the electrode assembly and includes an upper cladding covering the lower cladding, wherein each of the upper and lower claddings is a metal layer formed of different rigid metals and the pouch cladding has a sealed edge.

Description

Pouch-type secondary battery and method for manufacturing the same}

The present invention relates to a pouch-type secondary battery and a method of manufacturing the same, which can reduce deformation of the battery while maintaining the rigidity of the pouch for secondary batteries.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. A secondary battery is a battery capable of repeating charging and discharging because reciprocal conversion between chemical energy and electrical energy is reversible. The secondary battery pouch refers to a laminated film case that protects a positive electrode, a negative electrode, a separator, and an electrolyte, which are main components of a secondary battery.

In general, the secondary battery pouch is composed of a multi-layer structure of a polymer layer/metal layer/polymer layer, moldability, heat fusion resistance, chemical resistance (electrolyte resistance/corrosion resistance), insulation, mechanical strength, oxygen and moisture barrier properties, etc. Is required.

Secondary battery pouches are mainly used as exterior materials for lithium ion polymer batteries or electric double layer capacitors. In particular, it is necessary to secure long-term durability of 10 years or more in order to be used as a battery for an automobile or an energy storage system (ESS).

Accordingly, research on a pouch exterior material for improving the mechanical stability of a pouch-type secondary battery as in Korean Patent Publication No. 2017-0101650 is continuing.

One aspect of the present invention provides a pouch-type secondary battery having increased mechanical properties by using a pouch exterior material for a secondary battery including a heterogeneous metal layer.

Another aspect of the present invention provides a method of manufacturing the pouch type secondary battery.

According to one aspect of the invention, the present invention is an electrode assembly; And a pouch exterior material receiving the electrode assembly and sealing the edge, wherein the pouch exterior material includes a lower exterior material on which the electrode assembly is placed; And an accommodating portion accommodating at least a portion of the electrode assembly, and including an upper casing covering the lower casing, wherein the upper casing and the lower casing each include metal layers formed of different rigid metals, and the pouch casing. Provides a pouch type secondary battery with a sealed edge folded.

According to another aspect of the invention, the present invention comprises the steps of receiving the electrode assembly in the lower exterior material; Sealing the upper exterior material that accommodates the electrode assembly and covers the lower exterior material with the lower exterior material; And folding the sealed edge, and the upper and lower casings each provide a pouch-type secondary battery manufacturing method comprising metal layers formed of different rigid metals.

The pouch-type secondary battery according to the present invention can improve the mechanical properties of the battery, so that when using the battery, the shape of the battery can be reduced. Therefore, a battery having a high capacity and a high energy density can be developed.

1 is a schematic view showing a folded edge of a pouch-type secondary battery manufactured according to an embodiment of the present invention, and a top view of a pouch-type secondary battery with folded edges, and a bottom view of a perspective view.
Figure 2 shows an exemplary cross-sectional view of the top and bottom casing of the present invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention provides a pouch-type secondary battery including a pouch exterior material for a secondary battery capable of reducing deformation of the battery while maintaining the rigidity of the pouch for the secondary battery.

More specifically, according to an embodiment of the present invention, the present invention is an electrode assembly; And a pouch exterior material receiving the electrode assembly and sealing the edge, wherein the pouch exterior material includes a lower exterior material on which the electrode assembly is placed; And an accommodating portion accommodating at least a part of the electrode assembly, and including an upper casing covering the lower casing, wherein the upper casing and the lower casing each include metal layers formed of different rigid metals, and the pouch casing is Provided is a pouch-type secondary battery with a sealed edge folded.

The electrode assembly is not limited, as long as it is commonly used as a secondary battery, and is, for example, cross-stacked so that the surfaces coated with the electrode active materials of the cathode and the anode face the separator.

On the other hand, the electrode assembly is used to be stored in the pouch with substantially the electrolyte. The electrolyte may include lithium salts such as LiPF ₆ and LiBF ₄ in organic solvents such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Can. Furthermore, the electrolyte may be liquid, solid or gel.

Meanwhile, the upper and lower exterior materials may include an inner resin layer, a metal layer, and an outer resin layer, and components of each layer are as follows.

The inner resin layer may be a polyolefin such as polyethylene (PE) or polypropylene (PP) or a copolymer thereof. When polyolefins such as PE or PP or copolymers thereof are used for the inner resin layer, it is preferable because it has not only the properties required for a secondary battery pouch such as good heat sealing, moisture resistance, and heat resistance, but also good processability such as lamination. Do. The thickness of the inner resin layer is preferably 40 to 100 μm, more preferably 70 to 90 μm in consideration of formability, insulation, and electrolyte resistance. If the above range is not satisfied, a problem in that formability, insulation, and electrolyte resistance may be deteriorated.

As the material of the metal layer, a common one used in the art may be used, for example, selected from the group consisting of iron (Fe), chromium (Cr), manganese (Mn), nickel (Ni), and aluminum (Al). Can be one or more metals or alloys.

At this time, it is preferable that the metal layer used for the upper facing material and the lower facing material is formed of a metal having different rigidity. For example, the upper facing material includes a metal layer formed of soft aluminum, and the lower facing material is hard stainless steel. It may include a metal layer formed of.

As the lower exterior material, stainless steel may be austenite-based, ferrite-based, martensitic-based, and non-magnetic stainless steel may be used, but is not limited thereto. For example, SUS304, SUS430, SUS316, etc. may be used. Can.

As the upper exterior material, aluminum may use an aluminum foil, and more preferably, an aluminum foil containing iron may be used to further impart ductility to the aluminum foil. In the aluminum foil containing iron, the content of iron may include 0.1 to 9.0% by weight, and more preferably 0.5 to 2.0% by weight, based on 100 weight of the total aluminum foil. Can. When the iron content of the aluminum foil is less than 0.1% by weight, the degree of ductility that can be obtained by containing iron is insufficient, and when it exceeds 9.0% by weight, moldability is deteriorated.

It is preferable that the metal layer used for the upper and lower exterior materials is a metal layer having a low rigidity, and a thicker layer than a metal layer having a high rigidity. For example, when aluminum is used as the metal layer having low rigidity and stainless steel is used as the metal layer having high rigidity, the thickness of the aluminum metal layer may be 40 μm, and the thickness of the stainless steel metal layer may be less than 20 to 40 μm. That is, by using a metal layer having a high stiffness with a thin thickness, stiffness as in a conventional cell can be obtained.

On the other hand, when the thickness of the metal layer having high stiffness is thick compared to the thickness of the metal layer having low stiffness, it may be difficult to fold the edge as shown in FIG. 1, and the thickness of the metal layer having high rigidity is thin compared to the thickness of the metal layer having low rigidity. It is difficult to produce a pouch for a secondary battery and it can be difficult to maintain a folded shape.

Further, each metal layer used for the upper and lower exterior materials may be etched or degreased to improve the adhesion with the inner resin layer, but may be omitted to reduce process speed.

The thickness of the metal layer is preferably 10 to 100 μm, more preferably 30 to 50 μm, taking into account processability, oxygen and moisture barrier properties, and the like.

The outer resin layer may be made of a first outer resin layer and a second outer resin layer, and the first outer resin layer is polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized poly It is preferable to use a film made of polyester or nylon, such as ester or polycarbonate, and it is more preferable to use a nylon film having excellent burst strength, pinhole resistance, and gas barrier properties, as well as excellent heat resistance, cold resistance and mechanical strength. Do.

Specific examples of the nylon film include polyamide resins, that is, films such as nylon 6, nylon 66, a copolymer of nylon 6 and nylon 66, nylon 610, and metaxylenediamine (MXD6).

When laminating the first outer resin layer, the thickness of the stacked first outer resin layer is preferably 10 to 30 μm, and particularly preferably 12 to 25 μm. When the thickness of the first outer resin layer is less than 10 μm, physical properties are easily deteriorated, and when it exceeds 30 μm, moldability is deteriorated.

Furthermore, a second outer resin layer may be formed on the first outer resin layer to protect the battery from external impact and environment. The second outer resin layer may be used without particular limitations as long as it is commonly used as an exterior material. The second outer resin layer, like the first outer resin layer, polyester or nylon, such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, co-polymerized polyester, polycarbonate, etc. It is preferable to use a film of the like, and more preferably, PET can be used. The thickness of the second outer resin layer is preferably 5 to 30 µm, more preferably 10 to 20 µm in consideration of moldability and insulation. If the above range is not satisfied, a problem that moldability and insulation may be deteriorated may occur.

Furthermore, an adhesive layer for bonding each layer between the inner resin layer and the metal layer, between the metal layer and the first outer resin layer, and between the first outer resin layer and the second outer resin layer may be formed, for example A polyurethane-based or polyolefin-based adhesive layer may be formed.

In addition, the adhesive layer may include at least one heat dissipation filler selected from the group consisting of graphite, carbon fibers, carbon black, and carbon fillers having high thermal conductivity to dissipate heat generated inside the battery to the outside, but is not limited thereto. Does not.

On the other hand, it is possible to form a receiving portion capable of accommodating the electrode assembly in any one of the upper and lower sheathing material, the depth of the receiving portion may vary depending on the size of the electrode assembly to be accommodated. For example, the lower sheathing material has no receiving portion, and a receiving portion for receiving the electrode assembly may be formed only in the upper facing material.

Furthermore, when the housing is formed on both the upper and lower exterior materials, since the exterior material including the metal layer formed of a metal having low rigidity is more easily molded, the depth of the accommodation portion of the exterior material including the metal layer formed of a metal having low rigidity is , It is preferable that the depth compared to the depth of the receiving portion of the exterior material including a metal layer formed of a metal with high rigidity. For example, the depth of the receiving portion of the exterior material including the metal layer formed of the metal having low rigidity may be 100 to 500% of the depth of the receiving portion of the exterior material including the metal layer formed of the metal having high rigidity.

When the depth of the receiving portion of the exterior material including the metal layer formed of a metal having low rigidity is less than 100% of the depth of the receiving portion of the exterior material including a metal layer formed of a high rigidity metal, the energy density of the secondary battery is lowered, and 500%. If it exceeds, a problem may occur that the shape of the pouch is distorted due to residual stress during forming.

Furthermore, the pouch-type secondary battery may fold the edge portion of the pouch exterior material as shown in FIG. 1, and when the edge is folded as described above, it is preferable to fold the edge so that the exterior material including a high-stiffness metal layer is located outside.

When the exterior material including the metal layer having high rigidity is located outside, the shape of the pouch-type secondary battery may be kept constant after folding the edge of the exterior pouch exterior material, and the convex portion and the folded portion of the exterior pouch exterior material are prevented to prevent shape deformation. There is no need to glue the edges.

The degree of folding the edge is not limited, but it is desirable to fold the battery space efficiently. For example, the edge can be folded to be 90 degrees so that the edge is attached to the convex portion of the pouch exterior material, and when the edge is folded 180 degrees, it can be folded once more to be 90 degrees.

Furthermore, when the exterior material including the metal layer having high rigidity is located outside, the mechanical properties of the battery can be improved to prevent the shape deformation of the battery, and thus the swelling of the pouch is swollen due to the gas generated from the battery inside. ) Can prevent the phenomenon.

In another embodiment of the present invention, the present invention comprises the steps of receiving the electrode assembly in the lower exterior material; Sealing the upper exterior material that accommodates the electrode assembly and covers the lower exterior material with the lower exterior material; And folding the sealed edge, and the upper and lower casings each provide a pouch-type secondary battery manufacturing method comprising metal layers formed of different rigid metals.

In the step of sealing the upper facing material and the lower facing material, the sealing may be sealing by an adhesive, but sealing by heat is preferable since sealing by applying heat may increase resistance to peeling stress.

Sealing by heat may be performed at a temperature in consideration of characteristics of each material used in the secondary battery.

Furthermore, the step of folding the sealed edge is preferably performed so that the exterior material including the metal layer having high rigidity is located outside. As mentioned above, when the metal layer having high compatibility is located on the outside, the shape of the pouch type secondary battery may be kept constant after folding the edge of the pouch exterior material once, and the convexity of the pouch exterior material to prevent shape deformation This is because it is not necessary to bond the part and the folded edge with an adhesive, and swelling can be prevented.

Furthermore, when a swelling phenomenon occurs, swelling occurs in an exterior material including a relatively weak, low-stiffness metal layer, and thus may be useful for detecting a problem secondary battery. For example, the swelling phenomenon can be detected even when the sensor for sensing swelling is attached only to an exterior material including aluminum as a metal layer when manufacturing the secondary battery of the present invention.

Therefore, according to the present invention, the present invention enables the development of a battery having a high capacity and a high energy density, and the swelling phenomenon of the secondary battery can be suppressed, thereby preventing the deformation of the shape of the battery during the use period of the secondary battery. It is possible to provide a pouch-type secondary battery and a method for manufacturing the same.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are only examples for helping the understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

Production Example 1: Preparation of a pouch exterior material containing different types of metal

<Manufacturing of upper exterior materials>

A metal layer formed of aluminum was adhered to one surface of the inner resin layer formed of polypropylene. Then, a nylon film is laminated on the metal layer as a first outer resin layer, and a polyethylene terephthalate (PET) is laminated on the first outer resin layer as a second outer resin layer to produce a multilayer film for manufacturing an upper exterior material. It was prepared.

Polyurethane was used as an adhesive layer for adhering each layer between the inner numerical layer and the metal layer, between the metal layer and the first outer resin layer, and between the first outer resin layer and the second outer resin layer.

The multi-layer film produced above was molded to prepare an upper exterior material in which the receiving portion of the electrode assembly is present. At this time, the depth of the receiving portion of the upper exterior material was 4-10 mm.

<Production of lower exterior material>

In manufacturing the lower facing material, a lower facing material was manufactured in the same manner as the method for manufacturing the upper facing material, except that stainless steel was used as the metal layer and the depth of the receiving portion was 2 to 4 mm.

Production Example 2: Preparation of pouch type secondary battery

A secondary battery was manufactured using the upper and lower exterior materials prepared in Production Example 1.

At this time, an electrode assembly was placed in the receiving portion of the lower exterior material, and the lower exterior material was covered with the upper exterior material.

Thereafter, heat bonding was performed at 130 to 220° C. for 3 to 10 seconds using a plate so that the upper and lower exterior materials were adhered.

Then, after the upper facing material and the lower facing material were thermally bonded, the edges of the adhesive portion were folded as shown in FIG. 1 so that the lower facing material was positioned outside.

Although the embodiments of the present invention have been described in detail above, the scope of rights of the present invention is not limited thereto, and it is possible that various modifications and variations are possible without departing from the technical spirit of the present invention as set forth in the claims. It will be apparent to those of ordinary skill in the field.

10: outer resin layer
20, 40: adhesive layer
30: metal layer
50: inner resin layer

Claims (8)

Electrode assembly; And
Accommodating the electrode assembly, and includes a pouch exterior material with an edge sealed,
The pouch exterior material includes a lower exterior material on which the electrode assembly is placed; And an accommodating portion accommodating at least a portion of the electrode assembly, and including an upper casing covering the lower casing, wherein the upper casing and the lower casing each include metal layers formed of different rigid metals,
The pouch exterior material is a sealed edge folded, pouch-type secondary battery.
The pouch of claim 1, wherein the metal layer is one or more metals or alloys selected from the group consisting of iron (Fe), chromium (Cr), manganese (Mn), nickel (Ni), and aluminum (Al). Type secondary battery.
The pouch type secondary battery of claim 1, wherein the metal layer of the lower exterior material is formed of a metal having a higher rigidity than the metal layer of the upper exterior material.
The pouch-type secondary battery according to claim 1, wherein the metal layer of the lower exterior material is stainless steel, and the metal layer of the upper exterior material is aluminum or iron-containing aluminum.
The pouch type secondary battery according to claim 1, wherein the pouch case has a folded edge so that an exterior material including a metal layer having high rigidity is positioned outside.
Receiving an electrode assembly in the lower exterior material;
Sealing the upper exterior material that accommodates the electrode assembly and covers the lower exterior material with the lower exterior material; And
And folding the sealed edge,
The upper exterior material and the lower exterior material each comprises a metal layer formed of a different rigid metal, pouch type secondary battery manufacturing method.
The method of claim 6, wherein the sealing is performed by heat.
The method of claim 6, wherein the step of folding the sealed edge folds the edge so that the exterior material including the metal layer having high rigidity is positioned outside.

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